This invention pertains to arrangements for enhancing heat transfer from semiconductor power switching devices.
In solid state relays and power bridge circuits relatively high current power is conducted through semiconductor devices. The transfer of heat from such semiconductor devices is essential to their operation. Heat conducting, electrically insulating substrates have been advantageously employed to retain heat generating electrical components along a first substrate side while the opposite side of the substrate is mounted on a heat sink to permit the heat generated by the device to be dissipated at the external heat sink. In these arrangements, approximately 90% of the heat generated by the device is transferred through the substrate to the heat sink. The ability of these one sided heat transfer dissipation arrangements to transfer heat limits the use of these arrangements to lower power devices.
For high current, high power devices such as devices handling currents of 200 amps or higher, various arrangements have been provided to dissipate heat from two sides of the semiconductor device. In these arrangements, solder is ineffective to bond the device electrically because of the temperatures involved and a mechanical connection is made to the device. The device is clamped between two plates which act as electrical contacts and also function as heat sinks such that the device dissipates heat from both sides. These very high current arrangements are available commercially and one type is known as a press pack arrangement.
In certain circuit modules the currents are high currents and the heat to be dissipated is too high to permit compact construction using one sided heat dissipation but the amount of heat to be generated is not at the levels for which press pack construction is desirable.